Refractory faced blast furnace wear element

ABSTRACT

The invention pertains to a segmented wear element and supporting casting which is designed for installation within the stockline zone of a blast furnace, the wear element receiving the impact and abrasive wear of the furnace raw materials as they are dumped into the stockline zone. The wear element is a metal casting having a special abrasion resistant refractory cast into the wearing face. This wear element is arranged to engage with and be supported by a separate metal box casting which is fastened to the interior of the furnace shell. This supporting casting holds the refractory wear element in proper alignment with the refractory used in the lower linings of the furnace and avoids the use of other backing materials for the special refractory.

[ Oct. 16, 1973 United States Patent 1 Wilson REFRACTORY FACED BLAST FURNACE WEAR ELEMENT land,

75 Inventor: J oliriEfwilson, Grand Is Assignee: The Carborundum Company,

tion within the stockline zone of a blast furnace, the wear element receiving the impact and abrasive wear F n N Y of the furnace raw materials as they are dumped into t lagara a the stockline zone. The wear element is a metal cast- [22] Filed:

Jan. 3, 1972 ing having a special abrasion resistant refractory cast I into the wearing face. This wear element is arranged [21] Appl' 214987 to engage with and be supported by a separate metal box casting which is fastened to the interior of the furnace shell. This supporting casting holds the refractory wear element in proper alignment with the refractory used in the lower linings of the furnace and avoids the use of other backing materials for the special refractory.

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[56] References Cited UNITED STATES PATENTS 13 Claims, 8 Drawing Figures 915,601 3/1909 l-line et al. 266/31 Primary Examiner-Gerald A. Dost Att0rneyDavid E. Dougherty et al.

Patented Oct. 16,1973

I5 Sheets-Sheet 1 Patented Oct. 16, 1973 2 Sheets-Sheet 2 REFRACTORY FACED BLAST FURNACE WEAR ELEMENT BACKGROUND OF THE INVENTION The present invention relates generally to a blast furnace interior construction, and more particularly to blast furnace wear elements, several of which are disposed in a circumferential arrangement, around the interior of a blast furnace at the upper material-receiving end thereof to protect the blast furnace interior against the erosive effect resulting from the impact of descending charging material being introduced into the furmice. This part of the furnace is called the stockline zone.

A blast furnace conventionally includes an exterior metallic shell, an interior refractory lining adjacent the shell, and bell-type material-discharging means located at the top of the furnace. Material discharged into the furnace initially strikes the interior periphery of the furnace and is deflected inwardly toward a pile of previously introduced material (the furnace burden). Newly introduced material oftentimes rebounds off this pile and strikes the interior of the furnace a second time, at a lower location. If the furnace interior at the stockline zone is not protected against the erosive effect of both the initial and rebound impacts, the refractory lining inside the furnace will be worn away in a relatively short time, and the exterior shell will be exposed to the high temperatures of the furnace interior. Rapid erosion of the refractory lining requires frequent replacement, each replacement necessitating an expensive shi l-down of the furnace. Failure to replace worn refractory material in time will result in overheating of the exposed shell, thus weakening the shell which supports associated equipment and apparatus weighing about 160 tonsfhewiglit of which mayc aus collapse or buckling of the weakened overheated shell.

Although certain classes of super refractories have been developed which possess satisfactory erosion and abrasion resistance, these are quite expensive, considering the amount of special refractory needed. The major deterrent to the use of these refractories is the considerable thickness of refractory required to backup the working facel If clay brick back-up is used, there is a strong possibility that carbon deposition will soon make it useless as an unyielding support. If the special refractory is used to build up to full thickness, the cost becomes unjustifiably high. In addition, this high cost refractory section must be supported on a lower firebrick section which provides an uncertain support as it loses strength during extended furnace operation.

The principal object of the invention is therefore to utilize the abrasion resistance of special refractories without excessive bulk but providing positive support by using a box type of metal casting to support a suitable refractory wear element. Another object of the invention is to cast the metal around the refractory to hold it firmly in place in the wear element. A further object of the invention is to provide a means of attachment for the support of the wear element, said attachment means allowing rapid installation or removal of the wear element with minimum labor cost.

.These and other advantages of the invention will be more apparent by reference to the following FIGS. and detailed description.

SUMMARY OF THE INVENTION The invention pertains to a blast furnace having a shell, a lining and material discharging means at the top of the furnace and having a vertically disposed wear element extending along the vertical dimension of the area of initial and normal rebound impact of material discharged from the discharging means, the element having a front face and rear face, the front face being disposed toward the interior of the furnace. The element has engaging means on the rear face, the engaging means cooperating with support means attached to the furnace shell to mount and maintain the wear element in inwardly spaced vertical relation to the furnace shell. Inside the shell the element is in juxtaposition with one or more adjoining elements in relatively tightly abutting relation to form a circumferential wear resistant surface within the furnace.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a sectional view of the upper part of a blast furnace, showing the charging zone and stockline zone.

FIG. 2 is an enlarged view of one wall of the stockline zone, showing the wear element with special refractory and supporting metal casting in place.

FIGS. 3 and 4 show top and face views of the supporting metal casting.

FIGS. 5 and 6 show top and face views of the ceramic wear element.

FIG. 7 is a view of the rear or cold face of the wear element, showing the two mounting channel slots which engage the supporting metal casting.

FIG. 8 is a top view of a segment of the furnace shell at the stockline zone, showing the placement of the wear elements within the furnace shell.

DESCRIPTION OF THE INVENTION A sectional view of the upper part of a blast furnace is shown in FIG. 1. Here the stockline zone is shown in area 10 and it is in this area that the refractory lining suffers the most erosive shock and wear, caused by the initial and rebound impact of raw material charged into the top of the furnace through the material discharging means. It is apparent from the figure that the refractory lining must have a substantial thickness, as compared to the overall furnace diameter, to withstand the internal temperatures of the furnace. The refractory must be of sufficient thickness to protect the furnace outer shell 12 which gives structural support to the furnace, as well as parts of the furnace charging equipment. Below the stockline zone, the main function of the lining refractory is heat resistance, therefore, relatively inexpensive materials, such as fire-bricks of standard composition, may be used. For the stockline zone, special abrasion resistant refractories must be used. Refractory materials suitable for this purpose may comprise bonded or fused cast alumina, bonded silicon carbide, bonded aluminum silicate or fused cast mixtures of alumina, zirconia and silica. Furnacing tests have shown that refractory bodies using these materials provide superior performance when used in the stockline zone of a blast furnace. These refractories show much less wear than the fire-brick refractory which is used below the stockline zone. In present furnace construction, this fire-brick refractory supports the stockline refractory and as the fire-brick becomes weaker, the stockline refractory may become dislodged, thereby losing its effectiveness as a support. However, due to its greater heat and erosion resistance, the layer of special refractory in the stockline zone can be of substantially less thickness than that of the fire-brick refractory. The invention therefore provides a wear element which enables the use of thinner layers of refractory while providing a structure for independent support of the refractory.

The supporting structure for the refractory wear element is shown in FIGS. 2, 3 and 4. This structure is a box casting 16 which supports the wear element 17. The box casting 16 is attached to the interior of the furnace shell 12 by means of suitable bolts 20. For additional support, the box casting 16 may rest upon a triangular casting 22 which is also bolted to the interior of the furnace shell by bolts 24. Both castings can be made of ductile heat resistant iron or steel, since they are positioned in the upper part of the furnace, where temperatures are below the iron fusion point. Additional protection is furnished by the refractory layers 26 and 18.

The supporting box casting is shown in greater detail in FIGS. 3 and 4. The casting is designed to be attached to the furnace shell 12 by suitable bolts 20. The wear element 17 (see FIGS. and 6) may then be attached securely to the support casting by the slidable engagement of one or more vertical channel slots 19 on the rear or cold face of the wear element (See FIG. 7) with one or more corresponding vertical ribs 21 projecting inwardly from the supporting casting 16. This construction facilitates installation or replacement of the refractory wear elements within the furnace. Labor costs are reduced, since ordinarily only the wear element is handled while the supporting casting remains in place.

Top and front views of the wear element are shown in FIGS. 5 and 6. The refractory face of the element is made up of one or more refractory blocks 18, disposed with joints of about A to inch width between the blocks. These joints are filled with the same casting metal as that comprising the main body 17 of the wear element. The casting metal thus supports the refractories and bonds them firmly in place within the wear element. This refractory bearing area is defined as the front face of the element, this face being disposed toward the interior of the furnace. The refractory blocks may project slightly from the surface and function therefore to resist shock and abrasion. The casting metal of the wear element may be a ductile heat resistant iron or steel and the element is cast in a tapered form, the rear face having a substantially greater width than that of the front face, the relative differences in width depending on the radius of curvature of the furnace shell. This construction is made apparent as shown in FIG. 8, wherein a top view of the furnace shell shows the placement of the several wear elements in tightly abutting relationship to form a circumferential wear resistant surface within the furnace. In FIG. 2, the function of the support casting and wear element is seen clearly in that this combined structure acts to support a relatively thin layer of the abrasion resistant refractory in alignment with the refractory layer below the stockline, thus allowing proper charging of the furnace while still eliminating a substantial amount of expensive special refractory. Since the casting of the invention provides an independent support for the refractory wear element, this element remains in place for long periods of time and will not be affected by any shrinkage or weakening of refractory below the stockline zone.

The wear element of the invention has been described as formed by casting the metal directly around the refractory blocks, thereby bonding them within the metal matrix. While this procedure gives a strong bond between metal and refractory, thermal shock during casting may set up stresses in the refractory which causes cracking and spalling of the refractory surface. The different rates of expansion and contraction between the refractory and the surrounding metal also contribute to refractory stresses. To minimize these stresses, the refractory blocks are preferably coated before casting with a refractory material such as boron nitride paste, aluminum silicate cement or an alumi num silicate paper. This paper is approximately A inch thick, but may be used with a thickness ranging from about 3/32 to about 5/32 of an inch.

The refractory block is preferably coated with aluminum silicate cement and the aluminum silicate paper applied when the cement has partially dried. The paper adheres to the cement and the refractory block may then be placed in the mold for the casting of the bonding metal. The resulting bond is strong and the refractory remains relatively free of internal stresses.

What is claimed is:

1. In a blast furnace having a shell, a lining and material discharging means at the top of the furnace;

a. a vertically disposed wear element extending along the vertical dimension of the area of initial and normal rebound impact of material discharged from said discharging means, said element having a front face and a rear face, the front face being disposed toward the interior of the furnace, said wear element comprising a refractory faced metal casting, the refractory comprising at least one refractory block, the block being bonded to the wear element by the casting metal;

b. said element having engaging means on the rear face, said engaging means cooperating with support means attached to said furnace shell to mount and maintain the wear element in inwardly spaced vertical relation to the furnace shell; and

c. wherein the element is in juxtaposition with at least one adjoining element in relatively tightly abutting relation to form a circumferential wear resistant surface within the furnace.

2. A wear element according to claim 1 in which the refractory block is disposed to form a wear resistant surface upon the front face of the wear element.

3. A wear element according to claim 1 in which the refractory comprises materials selected from the group consisting of bonded alumina, fused cast alumina,

bonded silicon carbide, bonded aluminum silicate and' fused cast mixtures of alumina, zirconia and silica.

4. A wear element according to claim 1 in which the casting metal comprises ductile heat resistant iron.

5. A wear element according to claim 1 in which the casting metal comprises ductile heat resistant steel.

6. A wear element according to claim 1 in which the refractory block is protected against thermal shock during casting by coating materials selected from the group consisting of boron nitride paste, aluminum silicate cement and aluminum silicate paper.

7. A wear element according to claim 6 in which the coating material is aluminum silicate paper ranging from about 3/32 to about 5/32 inch in thickness.

11. A blast furnace according to claim 10 in which the second means comprises at least one vertical rib for slidably engaging at least one channel slot in the rear face of the wear element.

12. A box casting according to claim 10 in which the casting material comprises a ductile heat resistant iron.

13. A box casting according to claim 10 in which the casting material comprises a ductile heat resistant steel. 

2. A wear element according to claim 1 in which the refractory block is disposed to form a wear resistant surface upon the front face of the wear element.
 3. A wear element according to claim 1 in which the refractory comprises materials selected from the group consisting of bonded alumina, fused cast alumina, bonded silicon carbide, bonded aluminum silicate and fused cast mixtures of alumina, zirconia and silica.
 4. A wear element according to claim 1 in which the casting metal comprises ductile heat resistant iron.
 5. A wear element according to claim 1 in which the casting metal comprises ductile heat resistant steel.
 6. A wear element according to claim 1 in which the refractory block is protected against thermal shock during casting by coating materials selected from the group consisting of boron nitride paste, aluminum silicate cement and aluminum silicate paper.
 7. A wear element according to claim 6 in which the coating material is aluminum silicate paper ranging from about 3/32 to about 5/32 inch in thickness.
 8. A wear element according to claim 1 in which the rear face is substantially wider than the front face.
 9. A blast furnace according to claim 1 in which the engaging means for the wear element comprises at least one channel slot in the rear face of the wear element.
 10. A blast furnace according to claim 1 in which the support means comprises a box casting having a first means shaped to fit the furnace shell and a second means for engaging at least one channel slot in the rear face of the wear element.
 11. A blast furnace according to claim 10 in which the second means comprises at least one vertical rib for slidably engaging at least one channel slot in the rear face of the wear element.
 12. A box casting according to claim 10 in which the casting material comprises a ductile heat resistant iron.
 13. A box casting according to claim 10 in which the casting material comprises a ductile heat resistant steel. 